Self-winding membrane device
A device having a self-winding element is described. The self-winding element is built on a flexible membrane; it has an extended form and a retracted form. Stiffness in the extended form may be provided using membrane curvature, or a retractable support member may be used, or both. Transitions between the extended form and the retracted form are preferably accomplished using sequential activation of tensile members that are configured in segments of the membrane. Activation of the tensile elements is preferably implemented using a processor or controller that activates tri-state drivers in a predetermined sequence in order to pass a current through each element when heating is desired. A preferred material used for the tensile elements is thin film NITINOL.
Latest iBlaidZ, Inc. Patents:
This patent claims priority to U.S. Provisional Patent Application No. 61/490,422, filed on May 26, 2011, entitled “Self-winding Membrane Device”, the disclosure of which is hereby incorporated by reference in its entirety for all purposes.
TECHNICAL FIELDThis invention relates to devices that are wound or coiled and more particularly to self-winding membrane devices.
REFERENCES CITED
- “Thin film shape memory alloy microactuators”, Krulevitch, P. et. al., Journal of Microelectromechanical Systems, Volume 5, Issue 4, December 1996.
- “Hybrid Microcircuit Technology Handbook: Materials, Processes, Design . . . ”, James J. Licari et. al., 2nd edition, Noyes Publications, 1998, pp 82-84.
The size of electronic devices ranges from the very small to the very large. Gaming devices, portable data assistants (PDAs) and other portable computing devices, laptops, cell phone, smart phones, video players, music players, medical devices, and numerous other types of electronic devices are typically provided in sizes and shapes that are convenient for a user to hold, carry, and transport, for example, by being able to fit within a user's purse or pocket. For example, portable electronic devices are beginning to be used as personal computing platforms, combining computational power and communication capabilities with user convenience in a compact form. Typically such devices include a display used to present pertinent information to the user and, in some cases, the display surface can also be used as a touch sensitive input device. A popular form of such a portable electronic device fits comfortably in a shirt pocket.
Thin flat flexible sheets may be used as substrates for displays of electronic devices. For example, polyester (PET and PEN) films are available in many thicknesses such as 25 micrometers (1 mil) to 250 micrometers (10 mils). These films are flexible; for example they bend under gravity when draped over a shaped object.
Adding curvature to the geometry of a sheet makes it behave like a shell. A shell carries loads through a combination of “membrane response” and bending response. Membrane response or “shell response” can cause a shell to become relatively stiff.
Examples of curved shells include arched panels and cylindrical pipes. An egg shell also provides a good example of strength and response of a curved shell. When loaded primarily in “membrane mode” the egg shell is very strong. However, if loaded locally in bending, the load capacity is low and the shell may break.
Sputtered thin films of metal alloys comprising titanium and nickel known as NITINOL are capable of achieving high recoverable stresses of the order of 350 MPa, while having fatigue performance corresponding to thousands of cycles of actuation for the case of strain of approximately 3% or less, as described by Krulevitch et. al. New methods for fabricating thin film NITINOL at an attractive cost are under development, for example using Chemical Vapor Deposition, CVD.
Tantalum nitride (TaN) thin film resistors are rugged and stable; they have a typical sheet resistance of 100 ohms per square and good power-handling capabilities, as described by Licari et. al.
Despite the progress made in the displays and other components of electronic devices, there is a need in the art for improved devices and methods of making such devices.
SUMMARY OF THE INVENTIONDevices having a retractable element employing a flexible membrane substrate are disclosed. The retractable element has an extended form and a retracted form. It may be configured to be mechanically stable in the extended form by creating curved features in the membrane; these provide stiffening using the “membrane response”. The curved features are preferably achieved by heat forming or using attached thin film tensile elements. Alternatively, one or more support members may be provided to support an essentially planar element in extended form. A process for retracting the membrane into an enclosure may employ sequential activation of a first set of thin film tensile elements. Similarly, a process for extending the membrane for use as a display or other device may employ sequential activation of a second set of thin film tensile elements. The device may be integrated with a host or companion device, or it may be a stand-alone device having a wired or wireless link to a host device.
Various embodiments of the present invention are described hereinafter with reference to the figures. It should be noted that the figures are only intended to facilitate the description of specific embodiments of the invention. They are not intended as an exhaustive description of the invention or as a limitation on the scope of the invention. In addition, an aspect described in conjunction with a particular embodiment of the present invention is not necessarily limited to that embodiment and may be practiced in other embodiments. In this application, a membrane is defined as “a thin layer that is easily bent under normal circumstances”; the term “membrane” need not have a biological origin or basis. The use of curvature to stiffen the membrane is not a “normal circumstance”. “Easily bent” can be interpreted as bending under gravity when draped over a shaped object. PEN films are described merely as examples. Any membrane or film having a suitable flexibility, preferably having a flexural modulus in the range of 1-10 GPa, can be used. Polyester (PET) films and polyimide (PI) films may be suitable, depending on cost and temperature performance requirements for example. A cooling device may employ a metallic foil as the membrane for example. Membrane flexibility is desired for ease of manipulation during extension and retraction. “Film” and “membrane” are terms that are used interchangeably herein. Extendable membrane elements may vary in size from microscopic devices having their diagonal dimension measured in nanometers to meters. The extendable membrane elements may implement many useful functions, including but not limited to a display, a keyboard, a touch screen, a heating or cooling device, a screen for displaying a projected image, an antenna, or a sound-producing device. Furthermore, a useful device may comprise multiple film layers; wherein, for example, one or more layers comprises the self-winding capability described herein. The device may also incorporate multiple functions, for example, a display screen combined with a touch sensor.
The preferred method for supplying heat to activate the tensile elements, is to pass a current through them to create joule heating. An alternate method is to provide a resistive pad underneath or on top of the tensile element, the pad comprising a resistive material such as tantalum nitride, and provide current to the pad rather than directly to the tensile element. Close proximity of the pad and the tensile element may enable good thermal coupling between them.
Companies involved with the development of new display technologies such as Organic Light Emitting Diode (OLED) and Quantum Dot displays (QLED) have developed new substrates that can survive the required process temperatures while maintaining preferred optical, chemical, and physical properties. An exemplary material in this context is Poly Ethylene Naphthalate, PEN, developed by DUPONT TEIJIN FILMS. Another favored material capable of withstanding even higher processing temperatures is polyimide, such as KAPTON. Both of these materials have thermoplastic properties; i.e., they can be softened by heating and subsequently re-hardened by cooling. In contrast with thermo-setting materials, this cycle can be repeated. In the softened state, the material can be thermally formed, for example in a heat press. When cooled, thermo-formed thermoplastic materials such as PEN and polyimide are not rigid, but retain flexibility; this is required for a heat-formed display screen that is repeatedly coiled or uncoiled for example. PEN and PET (polyethylene terephthalate) and polyimide films typically have a flexural modulus in the range of 2-3 GPa, representing a desired level of flexibility (tendency to bend) for ease of winding the membrane into a coil having a small radius, desired for compactness in certain mobile devices for example.
In some contexts it may be beneficial to eliminate a winding spool and provide a means for tightly winding a membrane element to achieve a minimal outside diameter of the retracted form. When a rollable display or keyboard is integrated with a smart phone for example, it may be desirable for this outside dimension to be 1 cm or less.
In some contexts it may be beneficial to provide a simple retraction mechanism that is low in cost, by eliminating elements that are conventionally required, such as a spool with associated bushings, or a retraction motor with associated mechanical drive components and electrical driver circuits.
In some contexts it may be beneficial to provide a simple retraction mechanism that operates with low stresses applied to the membrane, especially during winding and unwinding operations, such that the mechanism can endure many thousands of deployment cycles.
In some contexts it may be beneficial to provide a fast method of retraction, enabling the use of effective strategies for improving drop performance. For example, if free-fall is detected by a sensor, the membrane may be retracted before the device hits the floor. For this strategy to be effective, a retraction time of a fraction of a second is desirable.
In some contexts it may be beneficial to provide a retractable element having aesthetic appeal. This may be accomplished by eliminating frames or braces that are typically required to support the membrane around its edges, or even more obtrusively in central areas. The aesthetic appeal may be desirable while providing a high-functioning element, not compromising on optical quality in the case of a display for example.
In some contexts it may be beneficial to provide a retractable element that is easily interfaced to a motherboard of a device, including both electrical and mechanical aspects. For example, active matrix organic light emitting diode (AMOLED) devices typically require more than 20 electrical signals to be routed between row-and-column driver circuits on a motherboard and individual pixels on a display.
Tri-state activation of tensile elements may be used in certain embodiments and will now be discussed. To activate tensile element 67a1 and its parallel neighbor 67a2, trace 65a is driven low (in voltage) while trace 65b is driven high, or vice versa. The current so produced in tensile elements 67a1 and 67a2 causes them to become hot through joule heating. The heat activates the localized portions of strips 48c1 and 48c2, and their combined tensile action causes the associated segment 51 to coil (curl up). Meanwhile the drivers connected to all of the other electrodes (such as 47c) are in their high-impedance state, and consequently no current flows in the other segments of strips 48c1 and 48c2. After segment 51 has coiled or has almost coiled, the driver connected to electrode 65a is turned off (transitions to the high-impedance state) via controller 25. Then trace 65c is driven by its associated tri-state driver to the correct voltage polarity to cause current to flow in tensile elements 67b1 and 67b2 of segment 52, causing these elements to heat, activating the tensile material, and causing this segment to roll up also. Following this sequence of tensile element activations, each of the segments is coiled in turn until membrane 14b achieves its fully retracted form, 14 of
While the present subject matter has been described in detail with respect to specific embodiments thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing may readily produce alterations to, variations of, and equivalents to such embodiments. Accordingly, it should be understood that the present disclosure has been presented for purposes of example rather than limitation, and does not preclude inclusion of such modifications, variations and/or additions to the present subject matter as would be readily apparent to one of ordinary skill in the art. For example, the concepts embodied herein can be applied to a portable device rather than a stand-alone device. Instead of a metal alloy the tensile elements may be formed from a shape memory material containing micrometer or nanometer scale fibers. Connections between the device and a companion device may be wired or wireless. A support member may be manually operated or motor driven; it may be directly or indirectly coupled to the extended element. The extendable element may be single or multi-function and single or multi-layered; for example it may include a display and a touch screen. If a telescoping or otherwise extendable support member is used, the extended membrane may not require any curvature; rather it may be essentially planar when deployed. An external stiffening member such as a rod or tube may be provided at the leading edge of the extended membrane. The retractable device may not be a display but rather a keyboard, a passive screen, a touch screen, a speaker for creating sound, an antenna, or may provide a carrier for another transducer or heating/cooling device, or may be any other flexible device having an extended form and a retracted form.
Claims
1. A device comprising:
- a retractable element comprising a flexible membrane;
- tensile elements positioned relative to the membrane such that sequential activation of the tensile elements extends the membrane to an extended form or retracts the membrane to a retracted form, wherein the tensile elements are heat activated, and
- a heat applicator configured to heat activate the tensile elements by passing electrical current through the tensile elements.
2. A device comprising:
- a retractable element comprising a flexible membrane; and
- tensile elements positioned relative to the membrane such that sequential activation of the tensile elements extends the membrane to an extended form or retracts the membrane to a retracted form, wherein the tensile elements are heat activated, and
- a film adjacent to the tensile elements and configured to heat activate the tensile elements using joule heating.
3. A device comprising:
- a retractable element comprising a flexible membrane;
- tensile elements positioned relative to the membrane such that sequential activation of the tensile elements extends the membrane to an extended form or retracts the membrane to a retracted form, wherein sequential activation of the tensile elements achieves the retracted form in less than a second; and
- a sensor to detect free fall of the device, and a processor executing instructions to control the sequential activation.
3744733 | July 1973 | Bennett |
3963854 | June 15, 1976 | Fowler |
4030775 | June 21, 1977 | Hill |
4200983 | May 6, 1980 | West et al. |
4587738 | May 13, 1986 | Kang |
4704798 | November 10, 1987 | Hird |
4903912 | February 27, 1990 | Coughlin |
4945650 | August 7, 1990 | Hird |
4972601 | November 27, 1990 | Bickford et al. |
4982910 | January 8, 1991 | Bickford |
5605312 | February 25, 1997 | Elder et al. |
5820057 | October 13, 1998 | Decarolis et al. |
6131844 | October 17, 2000 | Hsu |
6137454 | October 24, 2000 | Peck |
6276071 | August 21, 2001 | Khachatoorian |
6375165 | April 23, 2002 | Sherratt et al. |
6445290 | September 3, 2002 | Fingal et al. |
6550155 | April 22, 2003 | Hsu |
6762929 | July 13, 2004 | Sawyer |
7219709 | May 22, 2007 | Williams |
7344260 | March 18, 2008 | Derenski |
7415289 | August 19, 2008 | Salmon |
7426107 | September 16, 2008 | Yeh et al. |
7558057 | July 7, 2009 | Naksen et al. |
8220520 | July 17, 2012 | Lukos |
8548607 | October 1, 2013 | Belz et al. |
8590170 | November 26, 2013 | Wagner |
20050253775 | November 17, 2005 | Stewart |
20060060313 | March 23, 2006 | Lukos |
20060082518 | April 20, 2006 | Ram |
20060166713 | July 27, 2006 | Yeh et al. |
20060249091 | November 9, 2006 | Orbach |
20060266867 | November 30, 2006 | Critelli et al. |
20070153379 | July 5, 2007 | Mikkelsen et al. |
20080034604 | February 14, 2008 | Critelli et al. |
20080086925 | April 17, 2008 | Yang |
20080121349 | May 29, 2008 | De La Cruz |
20080144265 | June 19, 2008 | Aoki |
20080158795 | July 3, 2008 | Aoki et al. |
20080183307 | July 31, 2008 | Clayton et al. |
20080183316 | July 31, 2008 | Clayton |
20080204367 | August 28, 2008 | Lafarre et al. |
20080221715 | September 11, 2008 | Krzyzanowski et al. |
20080247126 | October 9, 2008 | Otsuka et al. |
20080289775 | November 27, 2008 | Lukos |
20080318633 | December 25, 2008 | Wong et al. |
20090051830 | February 26, 2009 | Matsushita et al. |
20090100599 | April 23, 2009 | Rawls-Meehan |
20090121660 | May 14, 2009 | Rawls-Meehan |
20090139663 | June 4, 2009 | Cutler |
20100007950 | January 14, 2010 | Yuzawa |
20100164973 | July 1, 2010 | Huitema et al. |
20100182738 | July 22, 2010 | Visser et al. |
20100231421 | September 16, 2010 | Rawls-Meehan |
20100243176 | September 30, 2010 | Cutler et al. |
20100246113 | September 30, 2010 | Visser et al. |
20100281441 | November 4, 2010 | Eldon et al. |
20110043479 | February 24, 2011 | van Aerle et al. |
20110071558 | March 24, 2011 | Dlugos et al. |
20110176260 | July 21, 2011 | Walters et al. |
20110213472 | September 1, 2011 | Clayton et al. |
20120002357 | January 5, 2012 | Auld et al. |
20120014054 | January 19, 2012 | Ashcraft et al. |
WO 2008/059345 | May 2008 | WO |
Type: Grant
Filed: May 22, 2012
Date of Patent: Feb 10, 2015
Assignee: iBlaidZ, Inc. (Mountain View, CA)
Inventor: Peter C. Salmon (Mountain View, CA)
Primary Examiner: Xiaoliang Chen
Application Number: 13/477,828
International Classification: H05K 7/00 (20060101);